[Sixty6Deluxe]

Hey all, fresh meat here looking for some wisdom. Got a 66 Chevelle Deluxe, installing new rad. Full disclosure, novice at best, my achilles has always been electrical, I read, pictures, watch videos, whiteboard.....nothing just goes over my head.

Working on the relay/double fans, I am now searching to tap an ignition source (low voltage) as main power is coming from Battery through relay. I've read 100 forums and end up more confused. I'm looking at the fuse box and am wondering is there a lead I can just plug into or do I need to splice into a wire. I thought oh the "Fused" spot next to Ign. looks nice and the Accessory Fused look wonderful. Does anyone know if a source in the fuse box would work & which one is best for this application?

Secondly, say the engine is to temp, sensor grounds and activates fans. I stop at 7-11, return w/slurpee 2 minutes later, key in ignition, turn key feeding power to relay which pulls power for fans (as temp is still at sensor ground level) causing loss of ample V to start the engine. Previous system was a simple fan direct to toggle switch in cabin (previous owner). If I forgot to switch off toggle to fan, turn key V would drop feeding fan, not enough to start engine. Trying to avoid this issue with the new system just not sure of a solution. I'd prefer to let the sensor do the work but will they pull when starting causing V drop in battery?

Any help would be appreciated.

 

[123pugsy]

Install your test light to the point of hook up choice.
First turn the key back to ACC to make sure it doesn't light up.
Then, turn it to run. It should light. Then, start, it should turn off while starting. This is the source you need.

 

[Hotwire]

Someone more familiar with 66s hopefully will chime in, but most ignitions have a start feature that will kill power to accessories when cranking to avoid your exact concern.

If you want to find the exact circuit you need, you have to have a test light.

Disconnect your battery first, my directions will have you working around the starter that has a straight feed to the battery, slip of the wrench and you'll be arcing, so disconnect the battery first.

Next, get to the starter and take a picture of the wires going to it. Next, remove the purple wire from the starter, wrap the electrical connection with tape. This is your start circuit wire, the ignition switch sends power to it to engage the starter. What we'll be doing it needs to be disconnected.

Reconnect your battery and get your test light. Ground it to something metal under the dash and make sure it works. Next, probe every available connection on your fuse panel. Find one that has no power with key off, and power with key on. Next thing is to test if it has power during cranking. Since you disabled the starter you can turn the key to start and nothing will happen. This way you can easily probe without worrying about starter / engine / battery. Once you find the connection, that's where you want to tie the turn on power for your relays.

Disconnect your battery, reinstall the purple wire, you can look back at the picture you took in case you forget where the wire goes, then reconnect the battery. You're done. 🤘

 

[64Elc]

You can also use a Ign hot source under your hood to trigger the relay if you have one. Just piggyback on it.
An elect choke would be one. Draw on the trigger wire is very low, milliamps.
Or jump the trigger wire from another relay with an ign hot trigger.
As pugsy says, don't use acc unless you want the fans on if at temp and you play the radio when stopping.

Better the fans not come on when starting but you should have enough amps to start your car even if the fans come on. If not your battery is weak, you have low amps going to the solenoid, or a poor starter hot connection. The starter is drawing maybe 300 amps so fan amps should not tip the boat.

If you want prevent the fans from running when starting a hot eng, not a bad idea, I think you could use a 5 pin relay as a "Master Trigger wire controller" using 87 and 87a to control the power out to the Fan Relay trigger with the trigger wire to the "MTWC" coming from your ign hot to starter solenoid but I have never done that and gotta think about it a little.

Relay expert out there?

Also, checking with Dakota Dig on their controller to see what that can do. I have one of their fan controllers which are really nice. Turns the fans on at adjustable temps, staggers the fans coming on, various functions, provision for a manual switch, AC. Maybe it does that, I'll find out and ask about the 5pin relay too.

 

[Sixty6Deluxe]

Someone more familiar with 66s hopefully will chime in, but most ignitions have a start feature that will kill power to accessories when cranking to avoid your exact concern.

If you want to find the exact circuit you need, you have to have a test light.

Disconnect your battery first, my directions will have you working around the starter that has a straight feed to the battery, slip of the wrench and you'll be arcing, so disconnect the battery first.

Next, get to the starter and take a picture of the wires going to it. Next, remove the purple wire from the starter, wrap the electrical connection with tape. This is your start circuit wire, the ignition switch sends power to it to engage the starter. What we'll be doing it needs to be disconnected.

Reconnect your battery and get your test light. Ground it to something metal under the dash and make sure it works. Next, probe every available connection on your fuse panel. Find one that has no power with key off, and power with key on. Next thing is to test if it has power during cranking. Since you disabled the starter you can turn the key to start and nothing will happen. This way you can easily probe without worrying about starter / engine / battery. Once you find the connection, that's where you want to tie the turn on power for your relays.

Disconnect your battery, reinstall the purple wire, you can look back at the picture you took in case you forget where the wire goes, then reconnect the battery. You're done. 🤘

Wowza, thanks I needed the 3rd grade version and that's exactly how you gave it to me. I'm going to do exactly this and I'll update so you know I didn't zap myself, lol. I can rebuilt XJ Transfer Case/Tranny, replace any suspension parts, remove drivers side axel shafts on E46's. Rebuilt 79 CB750's my brain mechanically understands all that but show me a wire diagram and my brain grounds itself. Seriously thanks.

 

[Sixty6Deluxe]

You can also use a Ign hot source under your hood to trigger the relay if you have one. Just piggyback on it.
An elect choke would be one. Draw on the trigger wire is very low, milliamps.
Or jump the trigger wire from another relay with an ign hot trigger.
As pugsy says, don't use acc unless you want the fans on if at temp and you play the radio when stopping.

Better the fans not come on when starting but you should have enough amps to start your car even if the fans come on. If not your battery is weak, you have low amps going to the solenoid, or a poor starter hot connection. The starter is drawing maybe 300 amps so fan amps should not tip the boat.

If you want prevent the fans from running when starting a hot eng, not a bad idea, I think you could use a 5 pin relay as a "Master Trigger wire controller" using 87 and 87a to control the power out to the Fan Relay trigger with the trigger wire to the "MTWC" coming from your ign hot to starter solenoid but I have never done that and gotta think about it a little.

Relay expert out there?

Also, checking with Dakota Dig on their controller to see what that can do. I have one of their fan controllers which are really nice. Turns the fans on at adjustable temps, staggers the fans coming on, various functions, provision for a manual switch, AC. Maybe it does that, I'll find out and ask about the 5pin relay too.

Thank you, my relay is a 5 pin, (87/87a/86/85/30) it came from Mishimoto for their Chevelle Direct w/ Shroud & 2-12" Fans. Imma try 64Elc's method so I can find that lead. Makes sense to disconnect the starter and cycle the ignition to find source. Once I locate the appropriate source can I verify output on the connection as well, do you know what multimeter setting one uses and what amps that lead should be getting.

 

[64Elc]

Hotwire, I read your post too fast. Yeah that sounds great. I'm going to check the same. Can't remember if my 64 shuts down accessories but I'm going to find out.
I can run that Start Defeat hot to my Dakota Digital controller power.

Sixry-Just use DC Volts on your VOM. A trigger pulls very low milliamps.

 

[RPS]

You could install a switch between source and relay, to turn it off.

 

[Sixty6Deluxe]

You could install a switch between source and relay, to turn it off.

It previously had a toggle. concerned w/adding it to the system as is it complicates things. Not necessary in the system but more in my head, once I add another factor to this issue, my brain keeps resetting. The previous toggle is already mounted in cabin, fan was ground to veh ground, fan hot to toggle, toggle tapped in to Ign. Fused on the box (no relay). When I pulled the hot off the fan it was crispy fried at some point. Still worked but the wire cover and sleeve were burnt. I'm thinking previous owner knew just about as much as I do.

 

[Sixty6Deluxe]

Hotwire, I read your post too fast. Yeah that sounds great. I'm going to check the same. Can't remember if my 64 shuts down accessories but I'm going to find out.
I can run that Start Defeat hot to my Dakota Digital controller power.

Sixry-Just use DC Volts on your VOM. A trigger pulls very low milliamps.

Understood, thank you!

 

[64Elc]

You can run a manual toggle in the cabin but splice it into the sensor Ground wire. Then if you want to turn the fans on it grounds the circuit as the sensor would and the fans come on.
Better way to go. That's how I wire a manual switch anyway.

 

[Hotwire]

Wowza, thanks I needed the 3rd grade version and that's exactly how you gave it to me. I'm going to do exactly this and I'll update so you know I didn't zap myself, lol. I can rebuilt XJ Transfer Case/Tranny, replace any suspension parts, remove drivers side axel shafts on E46's. Rebuilt 79 CB750's my brain mechanically understands all that but show me a wire diagram and my brain grounds itself. Seriously thanks.

You're welcome, wasn't sure how uncomplicated you needed, so I stepped through it. There's a multitude of guys on here that know wiring and will help out if the post catches their eye so you're in good hands.

As mentioned above if your ignition switch doesn't cut power to accessories there are ways to add a relay that will automatically cut power to the fans when cranking if you want, can lay out that design if you come back needing it.

 

[64Elc]

Hotwire
I would like to see that diagram. But I would want to cut the trigger, not main power.
I was drawing it out but couldn't get it.

Thanks

 

[Hotwire]

Hotwire
I would like to see that diagram. But I would want to cut the trigger, not main power.
I was drawing it out but couldn't get it.

Thanks

You'll need a 5 pin relay.
When the relay is at rest 87a and 30 are connected.
When the relay is energized 30 and 87 are connected, 87a gets disconnected.

Power from ignition will go through pin 30 so when the key is turned on the fans will fire if thermostat is grounded. When the starter purple wire is energized it kills power to the fan relay. After the car cranks it goes back to connecting 87a so the fans will operate normally.

 

[oldcutlass]

There are 3 flavors of power in your vehicle:
IGN - powered when the switch is in the run and start positions
ACC - powered when the switch is in run and ACC positions, but not in the start position
BAT - powered all the time.

 

[Jim Streib]

It might take some investigating but it seems to me years ago, or even different divisions of GM had ignition switches with an IGN1 and an IGN2 terminal (as well as the ACC/Accessory, SOL/Solenoid, and possibly a GND/Ground for gauge testing) and I wonder if IGN1 or IGN2 drops out while cranking ?.

This is off a GTO site and is labeled a little different but I have to wonder if something like that, if it does have the proper outputs to allow your fans to be triggered JUST when the key is in the "RUN" position, could it be retrofitted into your vehicle ?.

And then if it does work electrically, could the tumbler assembly be interchanged to keep your original key set up ?.

Jim

 

[64Elc]

Hotwire. Thanks. I'll see how I can apply that.

 

[Narti]

“Wowza, thanks I needed the 3rd grade version and that's exactly how you gave it to me. I'm going to do exactly this and I'll update so you know I didn't zap myself, lol. I can rebuilt XJ Transfer Case/Tranny, replace any suspension parts, remove drivers side axel shafts on E46's. Rebuilt 79 CB750's my brain mechanically understands all that but show me a wire diagram and my brain grounds itself. Seriously thanks.”

I feel your pain!!!

 

[Sixty6Deluxe]

Welp, down the rabbit hole I go!

First off thanks for all the information. All signs pointed to Acc Fused, so tested that line, tested just as you said. So I took off the after market radio lead and plugged the wire in (I'm going to splice the radio into the relay ignition wire which I will leave plugged in there. Took a deep breath, opened the Carb and whoosh she starts, Fear #1 gone, However the GEN light is now lit might be the battery it's a "21". I Let the Rad get to temp to burp. Got to 185-195 thermostat opened (burping procedures initiated) temp dropped, as it started to rise, both fans kicked on around 195-205 ish. I let her run another 10 minutes and shut it down as soon as the fans kicked on. Counted to 10 (not sure why) then started it to ensure the fans wouldn't draw on startup when temp was about 210. Started Right Up!!!!!! Fans followed a few seconds after Fear #2-46 gone. I ran her for a total of about 45 minutes parked, fans cycled on temp drop. At the end of 45 minutes shut down when fans came on again. Counted to 12 this time and started right up, fans start again after a few seconds. Seems like the car is following your instructions. I will road test, plus I'm sure she has to puke a little.

While this was going on I began testing the lights and other electronics. Headlights Check, Tailights Checks, Wipers Checks, Blinkers NOPE. Flippin Blinkers!!!!!! Got to thinking I got big hands and when I was removing the previous switch wiring I bet I knocked something out, look under the dash there's this really nice sky blue wire with a connector just dangling there. Could this be to the blinkers? if so doest one know where this bugger plugs in at? I took a backwards video under the dash I don't see a lead but maybe I was looking right at it.

 

[64Elc]

If you are pulling your trigger wire from Accessory on your fuse block you will be energizing your fan circuit when you turn your key to the Accessory position as well as Run position. You don’t want that. Pull your trigger from an Ign hot position on fuse block or an Ign hot wire in Eng compartment.